We employ a life-cycle model with income risk to analyze how tax-deferred individual accounts affect households' savings for retirement. We consider voluntary accounts as opposed to mandatory accounts with minimum contribution rates. We contrast add-on accounts with carve-out accounts that partly replace social security contributions. Quantitative results suggest that making add-on accounts mandatory has adverse welfare effects across income groups. Carve-out accounts generate positive welfare effects across all income groups, but gains are lower for low income earners. Default investment rules in individual accounts have a modest impact on welfare.